Fuel injection pump for internal combustion engines

ABSTRACT

A fuel injection pump has an inner chamber, a drive shaft extending into the inner chamber, a front cam plate setting a pump plunger into a reciprocating and rotating movement, a front face coupling which couples the drive shaft with the front cam plate, a roller ring provided with a plurality of rollers for supporting the cam plate, a rotational angle sensor including a stationary part and a sensor wheel formed as a movable part and arranged on the drive shaft radially opposite to the stationary part, a pivotable support ring having a part which axially overlaps the sensor wheel and carries the stationary part and a coupling part which couples the support ring with the roller ring and engages in a recess of the roller ring.

BACKGROUND OF THE INVENTION

The present invention relates to a fuel injection pump for internalcombustion engines.

More particularly, it relates to a fuel injection pump which has a driveshaft extending into an inner chamber and connected by a front facecoupling with a front cam plate which sets a pump plunger into areciprocating and rotating movement with the cam plate running onrollers of a roller ring, and a rotational angle sensor is provided inthe pump. Such a fuel injection pump is known from the DE-OS 33 36 871,in which the fixed sensor part is directly and firmly fixed to theroller ring and lies radially opposite the sensor wheel on the driveshaft. For purposes of centering, the fixed sensor part can be displacedand re-fixed in the circumferential direction on the roller ring. Thissolution has the disadvantage that there is play between the roller ringbearing and the fuel injection pump housing, allowing movement of theroller ring in its radial plain, when forces act upon it when cams ofthe cam plate ride up on the rollers. Due to the fact that the rollerring is adjustable via the injection timing bolt, the bolt represents aone-sided bearing point for the roller ring, so that when it is loadedby forces in its circumferential direction, the roller ring carries outtipping movements around the bolt fulcrum. Moreover, the bolt fulcrumitself also has play, and the bolt itself can give to a certain extent,via the injection timing gear, when loaded by forces at right angles tothe length of the bolt. On loading of the roller ring, its fulcrumadditionally performs a movement in the circumferential direction. Wherethe stationary sensor part is fixed on the roller ring, it performs thismovement in unison with the roller ring. For reasons of space andaccommodation, the stationary sensor is usually arranged diametricallyopposite the fulcrum point of the bolt. In this region, the movementcomponents of the roller ring are greatest during its movement aroundthe bolt. This then results in unintentional or erroneous measurementsdue to the fact that the stationary sensor part actually moves in acircumferential direction around the sensor wheel, and this causesincorrect timing of the fuel injection commencement. Depending onoperating conditions, this error accumulates, either positively ornegatively, causing the measuring result and the resultant injectioncommencement timing to be affected with an uncontrolled error. If thelogging of the revolutionary speed, which is required for the volumecalculation, lies within the relevant range, then this angle error hasthe effect of an error in the revolutionary speed, in turn making thevolume calculation wrong.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a fuelinjection pump of the above mentioned type, which avoids thedisadvantage of the prior art.

In keeping with these objects and with others which will become apparenthereinafter, one feature of the present invention resides, brieflystated, in a fuel injection pump in which, axially adjacent to thesensor wheel on the drive shaft, a support ring is pivoted and has apart axially overlapping the sensor wheel, on which part the stationarypart of the sensor is arranged, and the support ring is coupled with theroller ring via a coupling part which engages in a recess of the rollerring.

When the fuel injection pump is designed in accordance with the presentinvention, it has the advantage, that assisted by the support ring, themovement of the roller ring due to reactive forces of the cam drive canbe cancelled out in terms of measuring techniques, or at the very leastcan be rendered largely ineffective.

In accordance with another embodiment of the present invention, thecoupling part is arranged in the region between the bolt which engageson the roller ring and which lies opposite the stationary sensor part.Such a design provides for an advantageous arrangement of the couplingpart for the coupling of the support ring with the roller ring. It isstill another feature of the present invention that the coupling parthas a movement path which is determined by the radial guide faces of therecess. With such a construction the roller ring's own movements can bevirtually eliminated altogether with regard to the measuring position ofthe stationary sensor part, due to the reactive forces coming from thecam drive.

In accordance with another embodiment of the present invention, thecoupling part is a pin which protrudes at approximately 90° angularseparation radially from the bolt on the support ring and engages inradially aligned groove of the roller ring. Such a construction providesan arrangement of the coupling part which is easily located andmanufactured, and which is effective. The drive shaft can have a supportcollar which is bordered toward the coupling on the front cam plate sideby another collar and on which the sensor wheel can be radially andaxially secured and in which support ring can be guided such that it canbe turned between the sensor wheel and a part which runs onto the collaron the drive shaft side. The support ring can have parts which embracethe sensor wheel and which come to rest against it on the front facewhich faces away from the support ring. The drive shaft can have asupport collar which is internally bordered by a collar toward the frontcam plate side coupling and on which the sensor wheel is radially andaxially secured and the support ring is rotatably guided between thecollar and the sensor wheel. These features provide for advantageousbearing options for the support ring and its fixation in respect of themovement of the stationary sensor part relative to the sensor wheel.

The arrangement of the support ring having parts which embrace thesensor wheel is especially advantageous.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a partial section along the axis of the drive shaft of adistributor fuel injection pump with the parts arranged in accordancewith the invention,

FIG. 2 shows a partial section in accordance with the cross-section ofFIG. 1 in a first modified embodiment as a second embodiment example,

FIG. 3 shows a section in accordance with the cross-section in FIG. 1 ofa second modified form as a third embodiment example, and

FIG. 4 shows a partial section in accordance with the section in FIG. 1with a fourth embodiment example of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a partial section through a distributor fuel injection pumpalong the axis of its drive shaft 2, which is supported with plainbearings 3 in the wall of the housing 4 of the distributor fuelinjection pump, In its interior, the housing encloses a pump chamber 5,which is filled with pressurized fuel, The filling of the chamber isachieved by means of a delivery pump 6 which is driven by the driveshaft via a feather key 7 and which is inside the pump housing,

The end of the drive shaft has at its front face a claw pair 9, whichdrives a front cam plate 11 in a rotary motion via a carrier 10 and viaappropriate claws, which are not shown. A pump plunger 12 is coupled ina known manner with the front cam plate via a pin 14, which is held atthe front face by a spring 15 to rest against the front cam plate 11.The cams 16 of the front cam plate run over rollers 17, which aresupported in a roller ring 18 in a radial direction. With its circularouter contour, the latter is supported so as to be rotatable, in anappropriate cylindrical recess 19 of the pump housing, supporting itselfaxially via an apron 20 and its front face against a plate 21 whichcovers the delivery pump 6. The central breakthrough 22 of the rollerring is used to allow the claws 9 of the drive shaft to pass through,and for accommodating the coupling between the drive shaft and the pumpplunger with the carrier piece and the claws of the cam plate 11. In theregion of the apron 20, the roller ring, together with the plate 21,encloses a cylindrical space 23, into which the drive shaft 2 projects.This has a support collar 25, which is restricted against a final collar26 by the claw pair. This final collar has a larger diameter than thesupport collar and abuts on the front face 27 of the roller ring 18which borders the space 23. An intermediate disc 28 is further placedbetween the plate 21 and the support collar 25, closing off the supportcollar on the drive shaft side. Adjacent to the collar 26, a sensorwheel 30 is sweated onto the support collar in the space between theintermediate disc 28 and the collar 26, which is provided with teeth 31on its front face circumference. A support ring 33, which is rotatable,is arranged alongside the sensor wheel towards the intermediate disc 28and is axially secured between the intermediate disc 28 and the sensorwheel. The support ring has a ring wall 34 which axially encompasses thesensor wheel 30 and on which a stationary part 36 of a rotational anglesensor is arranged, which with its active side acts in conjunction withthe teeth 31 of the sensor wheel 30 and abuts opposite the latter in aradial direction. The stationary sensor part is connected via this cableconnection 39 with an electronic control unit, not shown here.

The support ring further has a radially projecting pin 41, whichprojects with as little play as possible into a groove 42 in the apron20 of the roller ring, thus serving the coupling of the support ringwith the roller ring. This pin is arranged at an angular separation of90° from the stationary sensor part 26 and, for reasons ofrepresentation, is included in FIG. 1 in a "laid-over" presentation.

The roller ring is rotatable in a known manner, by an injection timingplunger 43. To do this, the roller ring is coupled with the injectiontiming plunger 43 via a bolt 45 which extends radially towards the driveshaft. The bolt is fixed in the usual way in the roller ring and coupledby means of a pivoted connection with the injection timing plunger 43via a sliding block 46.

In the operation of the fuel injection pump, the drive shaft 2 is setinto a rotary motion, while at the same time, the delivery pump 6 is setin motion and the pump chamber 5 is supplied with pressurized fuel, thepressure of which depends on the number of revolutions. This fuel alsoacts on the injection timing plunger 43 against a return spring, notshown here, further adjusting this plunger as the rotational speedincreases. The resulting turning of the roller ring has the effect thatthe cam plate is set into its delivery stroke movement during riding upon rollers 17 at an ever earlier point in time. The pump plunger 12 ofthis distributor injection pump carries out several delivery strokes inthe usual way per revolution of the drive shaft, depending on the numberof fuel injection valves requiring to be supplied per revolution. Thecam plate 11 has several cams which also become active with the rollers17 which are distributed around the circumference of the roller ring.During the stroke of the cam plate against the force of the spring 15and the pressure prevailing in the pump working chamber in front of thepump plunger 12, there are forces acting on the rollers and the rollerring, which corresponding to the cam course also become effective incircumferential direction. This effects on the one hand a turn-backmoment on the injection timing plunger, whilst on the other hand causinga movement of the roller ring itself within its guide clearance in thecylindrical recess. However, if the roller ring is assumed to beretained on the bolt 45, then it can, by virtue of the play in theradial plain of the roller ring, tilt around the bolt as a fulcrum.Superimposed on this tilting movement is the play-affected connectionbetween the bolt 45 and the roller ring or the timing plunger. With eachdelivery stroke of the pump plunger, therefore, the roller ring carriesout transverse movements in its radial plain within the confines of thespecified play.

With normal pumps, this is not generally a problem. However,problems-will arise when the roller ring, as a stationary part of anangle sensor is required to determine the rotational position of amoving part of the angle sensor. The torsion undertaken by the injectiontimer for the adjustment of the injection commencement is to be fed backto an electrical control device, namely in relation to an imaginedrotational position of the drive shaft, which revolves synchronouslywith the cams of the cam plate. Seen in this way, the endeavour is toascertain to which points of the cam stroke curve, relative to the driveshaft which is driven synchronously with the speed of the internalcombustion engine, the injection takes place. In addition, the momentaryrevolutionary speed as required for the volume calculation, is to beascertained which, if it coincides with the "tilting" , can cause avolume error.

The movable part of the angle sensor, the sensor wheel 30, imparts tothe stationary sensor part 36 via the teeth 31, the revolution of thedrive shaft and the rotational angle distance, which is required by areference mark in order to achieve overlapping with the stationarysensor part, with the rotational angle position of the reference markrelative to the base cam being produced in a defined manner. If, asdescribed above, the stationary sensor part moves to and fro with theroller ring, then there will be no precise results. For this reason, thestationary sensor part 36 is arranged on the support ring 33, and thisis supported on the drive shaft and coupled to the roller ring in themanner described. The position of the coupling pin 41 at 90° separationfrom the clamping point on the bolt 45 which is diametrically oppositethe stationary sensor part 36, has the effect that in a tilting movementof the roller ring within the radial plain, the timing component in thecircumferential direction on the support ring becomes negligibly small.In this arrangement, both the avoiding movement of the roller ring inthe region of the bolt 45 and the tilting movement around the bolt 45 orthe injection timing plunger 43, are taken into account. In principle,the requirement is that the coupling pin should be arranged and alignedsuch that it is arranged and aligned on the roller ring axis in thedirection of the perpendicular of the bolt 45. The groove must thereforebe designed or arranged correspondingly.

In a variant of the embodiment example of FIG. 1, the pin 141 shown inFIG. 2, which corresponds to the pin 41 in FIG. 1, is provided with aspherical head 48, which projects with movement clearance into thegroove 42 of the roller ring 18. This has the advantage that the playbetween pin 41 and roller ring 18 can be kept smaller still, sincecompensation of alignment errors, in particular in the event of tiltingmovements of the roller ring 18, is still possible by means of the head48.

To guide the support ring 233 axially with greater measuring accuracy,the support ring in the embodiment example of FIG. 3 is fitted betweenthe collar 26 and the sensor wheel 30 with the least possible play andwith free movability in, the circumferential direction.

A more precise guidance is possible in accordance with the embodimentexample of FIG. 4, where the support ring on the ring wall 334 has parts50 which radially project inwards and embrace the sensor wheel 30 andwhich come to rest against that front face 51 of the sensor wheel whichfaces away from the support ring 333. Such overlapping parts 50 arearranged at several places dispersed around the circumference of thesupport ring 333, such that the sensor wheel 30 can still be insertedand then, together with the support ring, shrunk onto the support collar25. In this solution, an exact arrangement of the stationary sensor part36 in an axial direction to the sensor wheel 30 is ensured, enabling avery uniform sensor signal to be produced and fault influences from anaxial offset to be avoided.

The arrangement of the support ring 33, 233, 333 on the drive shaft 2has the advantage that the wear on the friction bearings 3 caused by theoperation of the pump and the consequential drive shaft tilting does notalter the separation between the sensor wheel 30 and the sensor part 36,so that the signal strength remains constant over the entire life.

The simultaneous axial arrangement makes it possible to reduce the widthof the sensor wheel 30 to a minimum (manufacturing advantages) withoutthe teeth --due to drive shaft axial play --being allowed to come out ofoverlapping to the active sensor part, which would also cause adeterioration of the signal strength.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofconstructions differing from the types described above.

While the invention has been illustrated and described as embodied in afuel injection pump for internal combustion engines, it is not intendedto be limited to the details shown, since various modifications andstructural changes may be made without departing in any way from thespirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can, by applying current knowledge,readily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this invention.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims.
 1. A fuel injection pump, comprisingmeans forming an inner chamber; a drive shaft having an axis andextending into said inner chamber; a front cam plate setting a pumpplunger into a reciprocating and rotating movement; a front facecoupling which couples said drive shaft with said front cam plate; aroller ring provided with a plurality of rollers for supporting said camplate; a bolt which sets a position of said roller ring; an injectiontimer connected with said roller ring; a rotational angle sensorincluding a stationary part, and a sensor wheel formed as a movable partand arranged on said drive shaft radially opposite to said stationarypart; a rotatable support ring extending completely around said axis andhaving a part which axially overlaps said sensor wheel and carries saidstationary part; and a coupling part which couples said support ringwith said roller ring and engages in a recess of said roller ring, saidstationary part of said sensor being located at one side of said axiswhile said coupling part is located at another opposite side of saidaxis.
 2. A fuel injection pump as defined in claim 1; and furthercomprising a housing which forms said inner chamber, said roller ringbeing pivoted in said housing.
 3. A fuel injection pump as defined inclaim 1, wherein said coupling part is arranged in a region between saidbolt and said stationary sensor part.
 4. A fuel injection pump asdefined in claim 1, wherein said recess of said roller ring has radialguide faces, said coupling part having a movement path which isdetermined by said radial guide faces of said recess.
 5. A fuelinjection pump as defined in claim 9, wherein said roller ring has aradial groove, said coupling part being formed as a pin which protrudesradially on said support ring at approximately 90° angular distance fromsaid bolt and engages in said radial groove of said roller ring.
 6. Afuel injection pump as defined in claim 5, wherein said pin has a headwhich is spherical and engages in said radial groove of said rollerring.
 7. A fuel injection pump as defined in claim 1, wherein said driveshaft has a support collar provided with a collar part facing saidcoupling, said support collar having a part located at a side of saiddrive shaft and arranged so that said support ring is rotatably guidedbetween said sensor wheel and said part of said support collar.
 8. Afuel injection pump as defined in claim 7, wherein said support ring hasa further part which embraces said sensor wheel and abuts against asurface of said sensor wheel which faces away from said support ring. 9.A fuel injection pump as defined in claim 1, wherein said drive shafthas a support collar with a collar part facing said coupling of saidfront cam plate, said sensor wheel being radially axially secured onsaid support collar, said support ring being rotatably guided betweensaid support collar and said sensor wheel.